Non-contact particle accelerator for blasting applications

ABSTRACT

A blast chamber having a plurality of blast assemblies, with each blast assembly comprised of a clocking mechanism having a particular geometric shape, a rotor assembly, and a power source. Each rotor assembly is capable of rotating about a center line axis and has a plurality of spaced-apart rotors. At least one rotor includes a generally central opening. The blast chamber further includes a grit intake source for introducing grit into each clocking mechanism and a power source to impart a rotational force to the each rotor assembly. The blast chamber also includes a blast area adjacent to each blast assembly. Grit is gravity fed from the grit intake source and into the clocking mechanism and directed via the particular geometric shape of the clocking mechanism while the rotors are rotating. The grit is then directionally hurled according to the shape of the clocking mechanism through the at least one central opening of the rotating rotors and out through the space between the individual rotors and at the adjacent blast area, which contains a steel plate or other metal in which blasting is desired. An optional shroud may cover a portion of each rotating assembly to divert incidental grit.

TECHNICAL FIELD

[0001] The present invention is generally directed to a non-contactparticle accelerator for use in blasting applications in order to prepmetal surfaces prior to painting or coating.

BACKGROUND OF THE INVENTION

[0002] Blasters are used to prep plate and shaped steel prior topainting or coating the steel. Blasters utilize steel grit that isforcibly directed at steel to achieve a “white metal” surface prior topainting or coating the steel. White metal surfaces are highly preferredby coating suppliers because white metal surfaces remove scale on thesurface of the steel and provide a “grippable” surface to which paintsand other coatings can readily adhere. By prepping steel to a whitemetal surface, paints and/or coatings can adhere to the steel surfacefor a long time. This technique is heavily used in marine applicationsand structures that have high impact regions (such as an aircraftcarrier deck) where the painted or coated surfaces are vulnerable tohigh wear and are expensive to replace.

[0003] Conventional blasters typically use a paddle arrangement in whicha wheel configuration having paddles or rotors forcibly blast or propelsteel grit onto a targeted steel surface. Because the grit can directlystrike the paddles or rotors, and the grit is designed to be highlyabrasive in order to achieve a white metal surface on the surface towhich the grit is directed, abrasion of the paddles is extremely high.In such applications, wear of the paddles and related components mayoccur in as little as 8-10 hours after commencement of the grit blastingand require replacement. The cost to replace the paddles can be in thethousands of dollars. Thus, down time and extremely high replacementcosts plague the current known blast systems.

[0004] Because of the extreme replacement cost with direct gritblasting, the industry has been often forced to run two passes at thesurface to which blasting is directed. The first pass includes forciblyblasting steel shot peen that creates a peened surface. Steel shot isrounder than the angular grit shot. The shot peening creates less wearon blasting components such that the replaceable wear is at 40-50 hoursof application, as compared to the grit blasting wear of 8-10 hours.However, shot peening creates a cratered but relatively smooth surfacethat is not conducive to paint or coating adherence. As such, blastingapplications traditionally apply a two part blasting process: a firstshot peening pass to removed most of the scale or other material, andthen a second grit pass to create the final surface. The two passprocess is expensive because it is time-consuming and requires morelabor, equipment, and supplies, and wear of the blasting parts is lessthan every 40-50 hours.

SUMMARY OF THE INVENTION

[0005] The present invention is directed to a new apparatus and processfor blasting steel to a white metal surface prior to the application ofpaints/coatings with vastly reduced wear over conventional blasters andeliminates the need for multiple blasting passes during the blastingprocess. The blast apparatus or assembly essentially operates as aparticle (grit) accelerator with little to no contact with wear surface.In one embodiment, the blast assembly includes a plurality ofspaced-apart rotors capable of rotating about a centerline axis of ashaft, where at least one of the rotors has a generally central openingaxially-aligned of the shaft. The assembly further includes a clockingmechanism having a particular geometric shape for accelerating anddirecting the grit or shot into the at least one generally centralopening and out through at least one space between the rotors. Theassembly also includes a power source that provides a rotating force tothe rotor assembly and a grit intake device that directs grit to theclocking mechanism. Preferably, the assembly also includes a shroud fordiverting incidental grit or shot.

[0006] The present invention is further directed to a new blast chambercontaining a plurality of blaster assemblies with the rotor assembliesfrom which grit is hurled toward an adjacent blast area that can receivea steel plate or other metal sheet in which a surface of the plate is tobe prepped. The blast chamber may include a grit intake chamber and gritcollector system that is capable to recycling the used grit andredirecting the grit back into the grit intake chamber.

[0007] The present invention further includes a method of obtaining awhite metal surface on a steel plate to which paint/coating is to beapplied. The method includes applying grit to a metal surface via ablaster that pulls in grit through a grit intake source into a clockingmechanism that directs grit into a rotor assembly or a plurality ofrotor assemblies, where each rotor assembly has a plurality ofspace-apart rotors. Each or most of the rotors include a generallycentral opening through which a portion of the clocking mechanismextends. Grit is directed from the clocking mechanism and hurledsubstantially parallel to the rotors and within the space between therotors along boundary layers of the rotor surfaces in an angularacceleration path onto the surface of the metal. The grit is directed ina particular path such that it is designed to not contact the surfacesof the rotors and makes incidental contact with a shroud, if present, tosignificantly reduce wear on the rotors and other working components.

[0008] These and other features and benefits will be discussed infurther detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Like reference numerals are used to designate like parts throughthe several views of the drawings, wherein:

[0010]FIG. 1 is a schematic diagram of the blasting assembly of thepresent invention illustrating the grit intake source, clockingmechanism, power source, rotor assembly, and optional shroud, in whichthe rotor assembly is directed at a targeted surface;

[0011]FIG. 2 is a schematic section view of the rotor, shroud, andclocking mechanism of the blasting assembly of FIG. 1 directed at asteel plate surface;

[0012]FIG. 3 is an enlarged schematic view showing the flow path of gritaccelerated and directed by the geometric shape of the clockingmechanism and hurled into the rotor assembly through openings in theindividual rotors and being hurled into the space between the individualrotor blades along boundary layers adjacent surfaces of the rotors;

[0013]FIG. 4 is a section view taken substantially along lines 4--4 ofFIG. 3 and better illustrates the angular acceleration path of the gritdirected from the clocking mechanism, along the boundary layers adjacentthe rotor surfaces and onto a targeted surface;

[0014]FIG. 5 is a front view of a single blaster assembly including arotor assembly, shroud, grit carburetor, clocking mechanism, and motor;

[0015]FIG. 6 is a right side perspective view of FIG. 5;

[0016]FIG. 7 is a left side perspective view of FIG. 5 betterillustrating one embodiment of the power source imparting a rotatingforce to the rotor assembly;

[0017]FIG. 8 is an exploded perspective view of the individual rotors,power source, shroud, clocking mechanism; grit, and grit carburetor;

[0018]FIG. 9 is a perspective view of the clocking mechanism;

[0019]FIG. 10 is a section view taken substantially along lines 10--10of FIG. 8;

[0020]FIG. 11 is a schematic diagram illustrating the blasting apparatusof a blast chamber along with grit collection apparatus;

[0021]FIG. 12 is a perspective view illustrating several blastingassemblies fixedly connected to a frame positioned adjacent a blastarea;

[0022]FIG. 13 is a perspective view like FIG. 12 better illustratingadditional frame structure of the blast chamber and a grit intakechamber;

[0023]FIG. 14 is a view like FIG. 13 and better illustrating additionalframe structure and exterior;

[0024]FIG. 15 is a top view of FIG. 13 and better illustrating the gritintake chamber with a device to assist direct grit into the gritcarburetors at each blast assembly;

[0025]FIG. 16 is a side elevation view of the blast chamber of FIG. 14shown less a portion of the frame exterior;

[0026]FIG. 17 is a perspective view of a piece of sheet steel with scaleabout to enter the blast area of the blast chamber of the presentinvention and with a “white metal surface” on at least one side of thesteel sheet after the blasting process;

[0027]FIG. 18 is a perspective view of a grit collector of the blasterthat is part of the bottom of the blast chamber;

[0028]FIG. 19 is a side view of an alternate embodiment rotor blade andshaft; and

[0029]FIG. 20 is an end view of the rotor blade of FIG. 19.

BEST MODE FOR CARRYING OUT THE INVENTION

[0030] The present invention is directed to apparatus and a method forblasting metal surfaces in order to remove scale and other material andto provide a white metal surface on the desired surface of the metal,such as steel, prior to coating or painting. The present invention is animprovement of the prior art because the key components of the blastingapparatus or assembly are designed to last many times longer than theprior art because the grit path is not designed to touch the surfaces ofthe system and reduced dust, as discussed in more detail below.

[0031]FIG. 1 is a schematic diagram of the basic blaster apparatus orassembly 10, which includes a grit intake source 12, a rotor assembly14, a power source 16, a clocking mechanism 18, and an optional shroud20. Grit 22 enters the grit intake source and is directed into the rotorassembly 14 in order to hurl (or blast) grit 22 onto a targeted metalsurface 24.

[0032] Now referring to FIGS. 2-8, which better structurally illustratethe features of the blaster assembly 10 of the present invention, therotor assembly 14 comprises a plurality of individual spaced apartrotors 26 (or blades) that are capable of rotating about a centerlineaxis 28 when a rotating force is applied directly or indirectly from thepower source 16. Each rotor, which according to a first embodiment is asmooth disk, includes a generally central opening 30 in which grit 22 isintroduced into the rotor assembly. Grit enters a grit intake source,such as a grit carburetor as shown, and is directed into the centralopenings of the individual rotors by the clocking mechanism 18. Theclocking mechanism is axially aligned with the central openings 30 ofthe rotors 26. Grit is directed by the clocking mechanism into thecentral openings of the rotating rotor assembly. Because the grit entersthe rotating rotor assembly, the grit is hurled outwardly of the rotorassembly within the space between the individual rotors along an angularacceleration path to the targeted surface.

[0033] Referring particularly to FIGS. 3 and 4, the present invention isbased upon boundary layer principles where grit is gravity fed into thegrit intake source, and directed into the clocking mechanism 18. Theclocking mechanism 18 extends into a least one central opening 30 of anindividual rotor 26 of the rotor assembly which is rotating at arelative high rate of speed, such as approximately 6000 rpm. The grit isdirected into the space between the rotors as illustrated in FIG. 3 andis angularly hurled outward from the clocking mechanism via the spacebetween the rotors along boundary layers 40 that are adjacent rotorsurfaces 42. The hurled grit is directed at the targeted surface towhich the white metal surface is desired.

[0034] Now referring particularly to FIGS. 5-8, the rotor assembly maybe like that disclosed and claimed in my co-pending patent applicationSer. No. 10/285,116, filed Oct. 30, 2002, and entitled “Mixer”. A shaft32 to which at least one outer rotor 26 is connected is directly orindirectly connected to the power source 16, such as a motor with a beltand sieve configuration (FIG. 7), in order to impart a rotating force toshaft 32 such that rotor assembly 14 rotates about central axis 28. Theshaft may be connected to only one end of the rotor assembly, or mayextend axially through the central openings of the individual rotors.The clocking mechanism 18 may be adjacent and parallel to the shaft 32,such as illustrated in FIG. 8. A plurality of spacers 34 (two per rotorare shown for illustrative purposes) between each rotor keep theindividual rotors spaced apart as well as to provide a connecting meansfor each rotor to the overall assembly.

[0035] Referring also to FIGS. 9 and 10, the clocking mechanismessentially directs the grit 22 into an area dictated by the particulargeometric shape of the clocking mechanism. In preferred form, theclocking mechanism may be like a piece of angle iron having asubstantially ninety degree angle when viewed in cross section of theclocking mechanism (FIG. 10). The effective grit flow within the centralopening 30 is reduced to a quarter circle 36 (although other geometricconfigurations may be used such as, but not limited to, octagonal,hemispherical, semi-circular, and triangular) in order to accelerategrit into the rotor assembly Grit 22 is then hurled from the rotorassembly through the space between the individual rotors is acceleratedalong a boundary layer 40 between rotor surfaces 42.

[0036] From the time that the grit exits the clocking mechanism andenters into the rotor assembly, the grit is not directed at any of therotor assembly surfaces, and, thus, wear of the surfaces is greatlyreduced over the prior art. However, there may be some incidentalcontact on to the spacers upon occasion. As such, the spacers 34 maypreferably be made of a hard steel with a hard anneal bushing and/orcovered with a gum rubber for increased life.

[0037] The shroud 20 may be added about a portion of each rotor assemblyto divert incidental grit or shot. Although the shroud is optional tothe integrity of the blasting assembly of the present invention, it ispreferably added to the assembly to not only divert incidental grit butprotects equipment from the contact with incidental grit and aids in thereduction of dust.

[0038] The power source is preferably a motor sized to impart rotationalforce to the shaft that rotates the rotor assembly. As such, the size ofthe motor is a function of the size and operational requirements of therotor assembly. However, to achieve the 6000 rpm for a blaster assemblysuch as illustrated and having a rotor diameter of 18″ to 36″, a 15 hpinduction motor may be used.

[0039] The invention further includes a complete blaster chamber 50 asschematically illustrated in FIG. 11. In addition to the blast assembly10, as discussed above, the used grit is collected and recycled back tothe grit source in order to minimize grit cost. As the blasting processmay use two tons of grit a minute, recycling of grit can be a great costreduction as well as dust reducer. In this embodiment, an auger 44 orother device may be employed that can drive the grit from the chambergrit intake source 47 into the individual blast assembly grit intakesource 12 and into the individual clocking mechanisms 18 prior to entryinto the rotor assembly. A steel plate 46, of which surface 24 is beingprepped in the blasting process, is brought into close proximity toouter edges 48 of the individual rotors 26. Grit that has already hitthe surface 24 drops to the bottom of a blast chamber 50. At the bottomof the blast chamber 50 is a collection bin or bucket 52. Another auger54 may be employed to drive the grit to a grit return path 56 that willeventually take the grit to the grit intake source 12. In this way, gritis recycled to be used over a long period of time.

[0040] Referring now to FIGS. 12-16, the blast chamber 50 includes aplurality of blast assemblies 10, which are placed in a configuration toensure the entire surface 24 of the steel plate 46 has grit directed toit. For example, a typical steel plate having dimensions of10′6″×1-½″×40′ might require eight blasting assemblies arranged intofour rows and two columns all with the shrouds 20 open in the same planeP as best illustrated in the FIG. 12. The steel plate 46 would enter ablast area 58, where the surface 24 of steel plate 46 would be adjacentand exposed to the open shroud rotors in plane P.

[0041]FIGS. 13 and 14 better illustrate frame enclosure 49 that housesthe blast chamber 50. The chamber grit intake source 47 is shown at thetop of the blast chamber 50 having an optional grit driver, such as anauger 44 which is illustrated in hidden lines in FIG. 13. Gritcollection bin 52 (which may be like that illustrated in FIG. 18) may bepositioned at the bottom of the blast chamber 50. Chamber exteriorsmembers 51 (such as steel plate) may be used to cover the chamber forsafety reasons as well as dust and noise reduction.

[0042]FIGS. 15 and 16 illustrate the grit intake source as viewed fromthe top of the blast chamber (FIG. 15) and how the grit is channeled orotherwise directed to the individual grit carburetors and clockingmechanisms of each blast assembly 10 (FIG. 16).

[0043]FIG. 17 best illustrates how a typical steel plate 46 is fed intoan opening 57 of the blast chamber 50 and exits the blast chamber in itsdesired prepped (“white metal”) form. Power rollers or chains (notillustrated) may be used to move the steel plate 46 through the blastarea 58 of blast chamber 50. The rate of movement will be determined bythe size of the steel plate, and the amount of “scale” that must beremoved in the blasting process. The configuration as shown in FIG. 17is designed to remove scale on a plate having dimensions of 10′6″×40′ ata linear rate of ¾″ to 2″ per second. Sensors (not shown) may be used todetermine when a plate is in the blast area and to signal to the powersource to stop until the a new plate has entered the blast area forblasting, which reduces power consumption and overall operating costs.Because the present blasting process does not require the two step shotpeening first pass and grit second pass of the prior art, the processincreases productivity and reduces in half the amount of time it takesto conventionally obtain a white metal surface on a similar size steelplate.

[0044] Although not illustrated in FIGS. 13-14, the frame structure mayhold another set of blast assemblies all with the clocking mechanismsand rotor assemblies directed at the blast area 58 in order to blastboth sides of the steel plate at the same time. Thus, for the blastchamber illustrated in the example of FIG. 13, there would be a total of16 blast assemblies with 8 to each side of the blast area.

[0045] Individual rotors may take on various forms, such as thosediscussed in my aforementioned co-pending patent application Ser. No.10/285,116, and which is incorporated herein by reference. Moreover, therotors may be “auger-like” in form, such as the rotor 26′ illustrated inFIGS. 19 and 20. In that embodiment, a single auger-like rotor may beused with out the central opening. The clocking mechanism will directthe grit in the space about the auger-like rotor and onto the adjacentsteel surface (not shown).

[0046] The present invention includes a process for obtaining a whitemetal surface that includes the blaster assemblies, and, preferably, theblast chamber, described above.

[0047] Advantages of the present invention include greatly increasingthe lifespan of blasting apparatus due to a lack of grit contact on wearsurfaces; reduction in material costs due to the systems grit recyclingcapabilities, reduction of grit dust given the generally self containednature of the blast chamber, and reduction of costly two-pass processingto achieve a white metal surface. The illustrated embodiments are onlyexamples of the present invention and, therefore, are non-limitive. Itis to be understood that many changes in the particular structure,materials, and features of the invention may be made without departingfrom the spirit and scope of the invention. Therefore, it is theApplicant's intention that his patent rights not be limited by theparticular embodiments illustrated and described herein, but rather bythe following claims interpreted according to accepted doctrines ofclaim interpretation, including the Doctrine of Equivalents and Reversalof Parts.

What is claimed is:
 1. A blast assembly comprising: a rotor assemblycapable of rotation about a centerline axis; said rotor assemblyincluding a at least one rotor having a boundary of space about the atleast one rotor; a power source capable of imparting a rotational forceto the rotor assembly; a grit intake device providing grit to a clockingmechanism having a particular geometric shape in order to directionallyhurl grit within the space about the at least one rotor.
 2. A blastassembly comprising: a rotor assembly capable of rotation about acenterline axis; said rotor assembly including a plurality ofspaced-apart rotors wherein at least one rotor contains a generallycentral opening; a power source capable of imparting a rotational forceto the rotor assembly; a grit intake device providing grit to a clockingmechanism, which is axially-aligned with the at least one generallycentral opening; said clocking mechanism having a particular geometricshape in order to directionally hurl grit out of the generally centralopening and through the space between at least two adjacent individualrotors.
 3. The blast assembly according to claim 1 further comprising ashroud that surrounds a portion of the rotor assembly.
 4. The blastassembly according to claim 2 further comprising a shroud that surroundsa portion of the rotor assembly.
 5. The blast assembly according toclaim 1 wherein the rotor is in the shape of modified auger.
 6. Theblast assembly according to claim 2 wherein each rotor is a generallysmooth surfaced disk.
 7. The blast apparatus according to claim 2wherein there are four rotors.
 8. The blast apparatus according to claim3 wherein the shroud is positioned to leave an opening to onelongitudinal side of the rotor assembly.
 9. The blast apparatusaccording to claim 1 wherein the clocking mechanism's geometric shapesubstantially forms a ninety degree angle as viewed in lateral crosssection of the clocking device.
 10. The blast apparatus according toclaim 2 wherein the clocking mechanism's geometric shape substantiallyforms a ninety-degree angle as viewed in lateral cross section of theclocking device.
 11. A blast chamber comprising: a frame; a plurality ofrotor assemblies positioned within the frame, each said rotor assemblyhaving at least one rotor capable of rotation about a centerline axis,and a clocking mechanism that is co-axially aligned with the centerlineaxis in order to directionally accelerate and hurl material into a spaceabout the at least one rotor and out of the rotor assembly in aparticular accelerated path; a grit intake source that feeds grit intoeach clocking mechanism; and a blast area having at least an inlet of asize to receive a metal surface for blasting within the frame andadjacent the rotor assemblies such that the output of each rotorassembly is directed at the blast area.
 12. The blast chamber accordingto claim 11 wherein each rotor assembly has a plurality of spaced apartrotors with a generally central opening in at least one rotor, andwherein the clocking mechanism accelerates and hurls material into theat least one generally central opening and out through the space betweenat least two of the rotors.
 13. The blast chamber according to claim 11further comprising a grit collection system, said grit collection systemincludes a grit collection bin at the base of the blast area in which tocollect fallen grit, said grit collection system further includes aconduit in which to funnel grit back to the grit intake source.
 14. Theblast chamber according to claim 11, wherein the chamber issubstantially enclosed.
 15. The blast chamber according to claim 11wherein a shroud covers a portion of each rotor assembly.
 16. The blastchamber according to claim 11 wherein there are eight rotor assemblies.17. The blast chamber according to claim 11 wherein the grit collectionbin is a substantially v-shaped trough.
 18. The blast chamber accordingto claim 11 wherein the grit intake source further includes an auger inwhich to direct the grit from the grit intake source to each rotorassembly's clocking mechanism.
 19. A method for obtaining a white metalsurface on a piece of sheet metal, the process comprising: providing ablast assembly consisting of a rotor assembly capable of rotating abouta center axis and having a plurality of spaced-apart rotors with atleast one generally central opening, and a clocking mechanism having aparticular geometric shape; providing a power source to impart arotational force to the rotor assembly; providing a metal surface towhich a white metal surface is desired to be positioned adjacent theopening of the shroud; providing grit through a grit intake source to befed into the clocking mechanism; directing the grit through thegeometric shape of the clocking mechanism and hurling it into thegenerally central opening of the spaced apart rotors and outward of therotor assembly between at least one space between individualspaced-apart rotors.
 20. The method according to claim 19 wherein themetal surface is fed into the area adjacent the opening of the shroud ata linear rate of ¾ inch to 2 inches per second.
 21. The method accordingto claim 19 wherein the grit enters the grit intake source at a rate of2 tons a minute.
 22. The method according to claim 19 wherein the aplurality of blast assemblies are placed in a configuration tosimultaneously blast the adjacent metal surface all at the same time.23. The method according to claim 19 wherein at least a portion of therotor assembly is shrouded.